[SPARK-20343][BUILD] Add avro dependency in core POM to resolve build failure in SBT Hadoop 2.6 master on Jenkins
[SPARK-20343][BUILD] Add avro dependency in core POM to resolve build failure in SBT Hadoop 2.6 master on Jenkins

## What changes were proposed in this pull request?

This PR proposes to add

```
      <dependency>
        <groupId>org.apache.avro</groupId>
        <artifactId>avro</artifactId>
      </dependency>
```

in core POM to see if it resolves the build failure as below:

```
[error] /home/jenkins/workspace/spark-master-test-sbt-hadoop-2.6/core/src/main/scala/org/apache/spark/serializer/GenericAvroSerializer.scala:123: value createDatumWriter is not a member of org.apache.avro.generic.GenericData
[error]     writerCache.getOrElseUpdate(schema, GenericData.get.createDatumWriter(schema))
[error]
```

https://amplab.cs.berkeley.edu/jenkins/view/Spark%20QA%20Test%20(Dashboard)/job/spark-master-test-sbt-hadoop-2.6/2770/consoleFull

## How was this patch tested?

I tried many ways but I was unable to reproduce this in my local. Sean also tried the way I did but he was also unable to reproduce this.

Please refer the comments in https://github.com/apache/spark/pull/17477#issuecomment-294094092

Author: hyukjinkwon <gurwls223@gmail.com>

Closes #17642 from HyukjinKwon/SPARK-20343.

zuotingbing/spark,nilsgrabbert/spark,apache/spark,zhouyejoe/spark,actuaryzhang/spark,minixalpha/spark,maropu/spark,tejasapatil/spark,panfengfeng/spark,lxsmnv/spark,LantaoJin/spark,kissmetrics/spark,spark-test/spark,chuckchen/spark,rikima/spark,apache-spark-on-k8s/spark,vinodkc/spark,bOOm-X/spark,yanboliang/spark,shuangshuangwang/spark,chuckchen/spark,wzhfy/spark,taroplus/spark,pgandhi999/spark,witgo/spark,JoshRosen/spark,loneknightpy/spark,rednaxelafx/apache-spark,Aegeaner/spark,aosagie/spark,rednaxelafx/apache-spark,minixalpha/spark,markhamstra/spark,szhem/spark,stanzhai/spark,icexelloss/spark,vinodkc/spark,michalsenkyr/spark,xuanyuanking/spark,MLnick/spark,darionyaphet/spark,alunarbeach/spark,poffuomo/spark,gengliangwang/spark,akopich/spark,janewangfb/spark,HyukjinKwon/spark,alunarbeach/spark,ueshin/apache-spark,mahak/spark,esi-mineset/spark,srowen/spark,zhouyejoe/spark,BryanCutler/spark,chuckchen/spark,mike0sv/spark,narahari92/spark,jlopezmalla/spark,ConeyLiu/spark,dbtsai/spark,bdrillard/spark,tengpeng/spark,rikima/spark,dongjoon-hyun/spark,goldmedal/spark,byakuinss/spark,huang1900/spark,hvanhovell/spark,adrian-ionescu/apache-spark,WeichenXu123/spark,pgandhi999/spark,xflin/spark,alunarbeach/spark,jkbradley/spark,sahilTakiar/spark,chuckchen/spark,srowen/spark,facaiy/spark,kissmetrics/spark,jkbradley/spark,ConeyLiu/spark,mike0sv/spark,zero323/spark,techaddict/spark,ahnqirage/spark,sahilTakiar/spark,jkbradley/spark,goldmedal/spark,michalsenkyr/spark,kiszk/spark,skonto/spark,apache-spark-on-k8s/spark,witgo/spark,ericvandenbergfb/spark,markhamstra/spark,apache/spark,skonto/spark,loneknightpy/spark,rekhajoshm/spark,zuotingbing/spark,lxsmnv/spark,kiszk/spark,setjet/spark,akopich/spark,JoshRosen/spark,saltstar/spark,adrian-ionescu/apache-spark,UndeadBaneGitHub/spark,ueshin/apache-spark,brad-kaiser/spark,maropu/spark,ahnqirage/spark,mdespriee/spark,map222/spark,dongjoon-hyun/spark,vinodkc/spark,tejasapatil/spark,jlopezmalla/spark,shaneknapp/spark,ddna1021/spark,brad-kaiser/spark,chuckchen/spark,facaiy/spark,dbtsai/spark,witgo/spark,JoshRosen/spark,HyukjinKwon/spark,bdrillard/spark,bdrillard/spark,zero323/spark,cloud-fan/spark,wzhfy/spark,byakuinss/spark,nlalevee/spark,ioana-delaney/spark,shubhamchopra/spark,JoshRosen/spark,alunarbeach/spark,gengliangwang/spark,ajaysaini725/spark,hhbyyh/spark,holdenk/spark,patrick-nicholson/spark,WindCanDie/spark,rednaxelafx/apache-spark,aosagie/spark,zero323/spark,kissmetrics/spark,darionyaphet/spark,shuangshuangwang/spark,SHASHANKB/spark,taroplus/spark,bravo-zhang/spark,HyukjinKwon/spark,1haodian/spark,darionyaphet/spark,wangyum/spark,LantaoJin/spark,sureshthalamati/spark,dhruve/spark,rekhajoshm/spark,srowen/spark,xflin/spark,rezasafi/spark,gengliangwang/spark,mdespriee/spark,sahilTakiar/spark,actuaryzhang/spark,aosagie/spark,shubhamchopra/spark,zuotingbing/spark,SHASHANKB/spark,highfei2011/spark,actuaryzhang/spark,UndeadBaneGitHub/spark,apache-spark-on-k8s/spark,jiangxb1987/spark,HyukjinKwon/spark,wzhfy/spark,zuotingbing/spark,apache-spark-on-k8s/spark,skonto/spark,dhruve/spark,byakuinss/spark,1haodian/spark,goldmedal/spark,maropu/spark,guoxiaolongzte/spark,ConeyLiu/spark,xuanyuanking/spark,wangmiao1981/spark,holdenk/spark,mahak/spark,brad-kaiser/spark,ahnqirage/spark,zhouyejoe/spark,publicRoman/spark,szhem/spark,bdrillard/spark,zzcclp/spark,srowen/spark,shuangshuangwang/spark,narahari92/spark,eyalfa/spark,ahnqirage/spark,wangyum/spark,spark-test/spark,SHASHANKB/spark,andrewor14/spark,xuanyuanking/spark,someorz/spark,setjet/spark,map222/spark,taroplus/spark,markhamstra/spark,HyukjinKwon/spark,janewangfb/spark,debugger87/spark,stanzhai/spark,LantaoJin/spark,cloud-fan/spark,WeichenXu123/spark,wangyum/spark,nlalevee/spark,ahnqirage/spark,maropu/spark,nchammas/spark,bravo-zhang/spark,pgandhi999/spark,shubhamchopra/spark,shaneknapp/spark,sureshthalamati/spark,hvanhovell/spark,LantaoJin/spark,cin/spark,debugger87/spark,mike0sv/spark,apache-spark-on-k8s/spark,xuanyuanking/spark,loneknightpy/spark,cin/spark,dhruve/spark,map222/spark,patrick-nicholson/spark,facaiy/spark,shuangshuangwang/spark,zero323/spark,ericvandenbergfb/spark,rednaxelafx/apache-spark,saltstar/spark,aray/spark,aokolnychyi/spark,rekhajoshm/spark,sureshthalamati/spark,caneGuy/spark,darionyaphet/spark,jrshust/spark,mdespriee/spark,akopich/spark,nlalevee/spark,holdenk/spark,huang1900/spark,setjet/spark,actuaryzhang/spark,1haodian/spark,ron8hu/spark,nchammas/spark,someorz/spark,sahilTakiar/spark,taroplus/spark,matthewfranglen/spark,techaddict/spark,lxsmnv/spark,esi-mineset/spark,mahak/spark,debugger87/spark,ioana-delaney/spark,andrewor14/spark,BryanCutler/spark,highfei2011/spark,facaiy/spark,ptkool/spark,liyichao/spark,akopich/spark,zero323/spark,panfengfeng/spark,JoshRosen/spark,map222/spark,liyichao/spark,adrian-ionescu/apache-spark,poffuomo/spark,aray/spark,map222/spark,huang1900/spark,mzl9039/spark,1haodian/spark,nilsgrabbert/spark,lvdongr/spark,skonto/spark,actuaryzhang/spark,darionyaphet/spark,ConeyLiu/spark,dbtsai/spark,huang1900/spark,kevinyu98/spark,narahari92/spark,markhamstra/spark,debugger87/spark,Aegeaner/spark,kiszk/spark,publicRoman/spark,tejasapatil/spark,aokolnychyi/spark,HyukjinKwon/spark,hhbyyh/spark,ajaysaini725/spark,zhouyejoe/spark,lxsmnv/spark,ueshin/apache-spark,WindCanDie/spark,liyichao/spark,brad-kaiser/spark,ajaysaini725/spark,highfei2011/spark,debugger87/spark,saltstar/spark,guoxiaolongzte/spark,hvanhovell/spark,vinodkc/spark,spark-test/spark,narahari92/spark,loneknightpy/spark,saltstar/spark,ptkool/spark,kiszk/spark,milliman/spark,patrick-nicholson/spark,BryanCutler/spark,BryanCutler/spark,Aegeaner/spark,tengpeng/spark,rikima/spark,MLnick/spark,saturday-shi/spark,janewangfb/spark,dongjoon-hyun/spark,tejasapatil/spark,rikima/spark,michalsenkyr/spark,MLnick/spark,lxsmnv/spark,yanboliang/spark,gengliangwang/spark,UndeadBaneGitHub/spark,publicRoman/spark,patrick-nicholson/spark,panfengfeng/spark,shubhamchopra/spark,highfei2011/spark,ericvandenbergfb/spark,joseph-torres/spark,milliman/spark,zzcclp/spark,nlalevee/spark,techaddict/spark,byakuinss/spark,joseph-torres/spark,rezasafi/spark,pgandhi999/spark,darionyaphet/spark,ptkool/spark,tejasapatil/spark,liutang123/spark,zuotingbing/spark,kiszk/spark,eyalfa/spark,ericvandenbergfb/spark,dongjoon-hyun/spark,shuangshuangwang/spark,shubhamchopra/spark,srowen/spark,jiangxb1987/spark,panfengfeng/spark,minixalpha/spark,eyalfa/spark,WeichenXu123/spark,facaiy/spark,ConeyLiu/spark,dbtsai/spark,esi-mineset/spark,minixalpha/spark,liutang123/spark,kevinyu98/spark,saturday-shi/spark,highfei2011/spark,michalsenkyr/spark,byakuinss/spark,dbtsai/spark,ahnqirage/spark,poffuomo/spark,SHASHANKB/spark,BryanCutler/spark,caneGuy/spark,someorz/spark,bdrillard/spark,xuanyuanking/spark,icexelloss/spark,WeichenXu123/spark,xflin/spark,hvanhovell/spark,shubhamchopra/spark,esi-mineset/spark,jlopezmalla/spark,ConeyLiu/spark,darionyaphet/spark,jiangxb1987/spark,dhruve/spark,witgo/spark,nlalevee/spark,loneknightpy/spark,tejasapatil/spark,saltstar/spark,ron8hu/spark,liyichao/spark,SHASHANKB/spark,aray/spark,huang1900/spark,kissmetrics/spark,publicRoman/spark,taroplus/spark,stanzhai/spark,bravo-zhang/spark,aokolnychyi/spark,LantaoJin/spark,mzl9039/spark,michalsenkyr/spark,zhouyejoe/spark,maropu/spark,apache-spark-on-k8s/spark,ptkool/spark,andrewor14/spark,witgo/spark,maropu/spark,cin/spark,xuanyuanking/spark,spark-test/spark,joseph-torres/spark,holdenk/spark,tengpeng/spark,ericvandenbergfb/spark,bOOm-X/spark,szhem/spark,Aegeaner/spark,minixalpha/spark,taroplus/spark,narahari92/spark,saturday-shi/spark,adrian-ionescu/apache-spark,saturday-shi/spark,aokolnychyi/spark,WindCanDie/spark,chuckchen/spark,jkbradley/spark,vinodkc/spark,liutang123/spark,mahak/spark,wangmiao1981/spark,bravo-zhang/spark,wangmiao1981/spark,nchammas/spark,janewangfb/spark,rednaxelafx/apache-spark,wangmiao1981/spark,nchammas/spark,rekhajoshm/spark,srowen/spark,SHASHANKB/spark,nilsgrabbert/spark,zhouyejoe/spark,caneGuy/spark,milliman/spark,alunarbeach/spark,janewangfb/spark,liutang123/spark,chuckchen/spark,cloud-fan/spark,ddna1021/spark,ddna1021/spark,someorz/spark,jrshust/spark,nilsgrabbert/spark,huang1900/spark,spark-test/spark,guoxiaolongzte/spark,MLnick/spark,skonto/spark,icexelloss/spark,witgo/spark,apache/spark,wangyum/spark,yanboliang/spark,setjet/spark,publicRoman/spark,nchammas/spark,UndeadBaneGitHub/spark,MLnick/spark,icexelloss/spark,joseph-torres/spark,UndeadBaneGitHub/spark,aosagie/spark,WindCanDie/spark,saturday-shi/spark,bOOm-X/spark,tengpeng/spark,sureshthalamati/spark,map222/spark,ddna1021/spark,panfengfeng/spark,mahak/spark,shaneknapp/spark,publicRoman/spark,gengliangwang/spark,ahnqirage/spark,someorz/spark,goldmedal/spark,rikima/spark,caneGuy/spark,adrian-ionescu/apache-spark,bravo-zhang/spark,LantaoJin/spark,ueshin/apache-spark,guoxiaolongzte/spark,aokolnychyi/spark,markhamstra/spark,jrshust/spark,techaddict/spark,joseph-torres/spark,joseph-torres/spark,bOOm-X/spark,WindCanDie/spark,sahilTakiar/spark,szhem/spark,dbtsai/spark,adrian-ionescu/apache-spark,MLnick/spark,shaneknapp/spark,aray/spark,actuaryzhang/spark,BryanCutler/spark,aosagie/spark,gengliangwang/spark,nlalevee/spark,apache/spark,ioana-delaney/spark,kevinyu98/spark,mzl9039/spark,hhbyyh/spark,patrick-nicholson/spark,loneknightpy/spark,mike0sv/spark,kevinyu98/spark,zzcclp/spark,michalsenkyr/spark,jkbradley/spark,minixalpha/spark,highfei2011/spark,goldmedal/spark,apache/spark,liyichao/spark,huang1900/spark,kissmetrics/spark,loneknightpy/spark,vinodkc/spark,hhbyyh/spark,bravo-zhang/spark,akopich/spark,cin/spark,mike0sv/spark,janewangfb/spark,panfengfeng/spark,bOOm-X/spark,ajaysaini725/spark,brad-kaiser/spark,mzl9039/spark,rikima/spark,ueshin/apache-spark,rikima/spark,ConeyLiu/spark,zzcclp/spark,shubhamchopra/spark,zhouyejoe/spark,poffuomo/spark,shuangshuangwang/spark,stanzhai/spark,andrewor14/spark,srowen/spark,caneGuy/spark,zero323/spark,liutang123/spark,apache-spark-on-k8s/spark,bOOm-X/spark,WindCanDie/spark,dongjoon-hyun/spark,setjet/spark,alunarbeach/spark,andrewor14/spark,witgo/spark,ron8hu/spark,wangmiao1981/spark,sureshthalamati/spark,wzhfy/spark,cloud-fan/spark,spark-test/spark,poffuomo/spark,jiangxb1987/spark,jkbradley/spark,taroplus/spark,map222/spark,zuotingbing/spark,ron8hu/spark,ioana-delaney/spark,shuangshuangwang/spark,techaddict/spark,pgandhi999/spark,techaddict/spark,aokolnychyi/spark,holdenk/spark,eyalfa/spark,rednaxelafx/apache-spark,skonto/spark,BryanCutler/spark,szhem/spark,guoxiaolongzte/spark,kissmetrics/spark,jlopezmalla/spark,guoxiaolongzte/spark,sahilTakiar/spark,mdespriee/spark,JoshRosen/spark,bdrillard/spark,yanboliang/spark,dhruve/spark,lvdongr/spark,narahari92/spark,aray/spark,goldmedal/spark,eyalfa/spark,Aegeaner/spark,someorz/spark,1haodian/spark,dhruve/spark,milliman/spark,caneGuy/spark,setjet/spark,vinodkc/spark,spark-test/spark,kissmetrics/spark,setjet/spark,kevinyu98/spark,andrewor14/spark,cin/spark,JoshRosen/spark,akopich/spark,lvdongr/spark,ueshin/apache-spark,lvdongr/spark,holdenk/spark,ptkool/spark,esi-mineset/spark,tengpeng/spark,ajaysaini725/spark,1haodian/spark,cloud-fan/spark,patrick-nicholson/spark,xuanyuanking/spark,hvanhovell/spark,rednaxelafx/apache-spark,lxsmnv/spark,jlopezmalla/spark,rezasafi/spark,wzhfy/spark,debugger87/spark,publicRoman/spark,MLnick/spark,adrian-ionescu/apache-spark,yanboliang/spark,xflin/spark,mzl9039/spark,Aegeaner/spark,jiangxb1987/spark,patrick-nicholson/spark,skonto/spark,rezasafi/spark,lvdongr/spark,hvanhovell/spark,icexelloss/spark,milliman/spark,WeichenXu123/spark,ddna1021/spark,ddna1021/spark,techaddict/spark,dongjoon-hyun/spark,saltstar/spark,aosagie/spark,UndeadBaneGitHub/spark,bOOm-X/spark,sahilTakiar/spark,aray/spark,shaneknapp/spark,pgandhi999/spark,jrshust/spark,pgandhi999/spark,wangyum/spark,lvdongr/spark,kevinyu98/spark,aosagie/spark,liyichao/spark,mike0sv/spark,mdespriee/spark,hhbyyh/spark,tengpeng/spark,yanboliang/spark,holdenk/spark,zzcclp/spark,kiszk/spark,tejasapatil/spark,joseph-torres/spark,kevinyu98/spark,lvdongr/spark,dhruve/spark,guoxiaolongzte/spark,nilsgrabbert/spark,gengliangwang/spark,jlopezmalla/spark,zzcclp/spark,cloud-fan/spark,akopich/spark,eyalfa/spark,rekhajoshm/spark,aokolnychyi/spark,brad-kaiser/spark,WeichenXu123/spark,mzl9039/spark,mdespriee/spark,ajaysaini725/spark,saturday-shi/spark,kiszk/spark,xflin/spark,jkbradley/spark,apache/spark,liutang123/spark,ron8hu/spark,shaneknapp/spark,nilsgrabbert/spark,jlopezmalla/spark,mahak/spark,sureshthalamati/spark,ericvandenbergfb/spark,janewangfb/spark,wangyum/spark,michalsenkyr/spark,wangmiao1981/spark,hhbyyh/spark,nilsgrabbert/spark,stanzhai/spark,byakuinss/spark,hhbyyh/spark,xflin/spark,jrshust/spark,icexelloss/spark,nlalevee/spark,jiangxb1987/spark,markhamstra/spark,debugger87/spark,maropu/spark,milliman/spark,icexelloss/spark,ptkool/spark,WindCanDie/spark,rezasafi/spark,bdrillard/spark,cin/spark,stanzhai/spark,poffuomo/spark,goldmedal/spark,lxsmnv/spark,andrewor14/spark,ddna1021/spark,xflin/spark,wangmiao1981/spark,rekhajoshm/spark,dbtsai/spark,wangyum/spark,wzhfy/spark,eyalfa/spark,sureshthalamati/spark,ueshin/apache-spark,minixalpha/spark,liyichao/spark,someorz/spark,hvanhovell/spark,rekhajoshm/spark,ron8hu/spark,poffuomo/spark,jrshust/spark,shaneknapp/spark,mahak/spark,rezasafi/spark,cin/spark,bravo-zhang/spark,jrshust/spark,zuotingbing/spark,ioana-delaney/spark,saturday-shi/spark,mike0sv/spark,szhem/spark,1haodian/spark,caneGuy/spark,byakuinss/spark,nchammas/spark,actuaryzhang/spark,liutang123/spark,LantaoJin/spark,HyukjinKwon/spark,stanzhai/spark,esi-mineset/spark,markhamstra/spark,yanboliang/spark,szhem/spark,nchammas/spark,saltstar/spark,tengpeng/spark,WeichenXu123/spark,jiangxb1987/spark,aray/spark,dongjoon-hyun/spark,zero323/spark,ron8hu/spark,highfei2011/spark,ioana-delaney/spark,mzl9039/spark,rezasafi/spark,zzcclp/spark,facaiy/spark,esi-mineset/spark,mdespriee/spark,brad-kaiser/spark,panfengfeng/spark,facaiy/spark,ericvandenbergfb/spark,SHASHANKB/spark,cloud-fan/spark,ioana-delaney/spark,narahari92/spark,wzhfy/spark,milliman/spark,Aegeaner/spark,alunarbeach/spark,apache/spark,ajaysaini725/spark,UndeadBaneGitHub/spark,ptkool/spark